sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

12 files changed, 446 insertions, 0 deletions

diff --git a/arch/xtensa/boot/dts/Makefile b/arch/xtensa/boot/dts/Makefile
new file mode 100644
index 000000000..7271294ce
--- /dev/null
+++ b/arch/xtensa/boot/dts/Makefile
@@ -0,0 +1,13 @@
+#
+# arch/xtensa/boot/dts/Makefile
+#
+# This file is subject to the terms and conditions of the GNU General Public
+# License.  See the file "COPYING" in the main directory of this archive
+# for more details.
+#
+#
+
+dtb-$(CONFIG_OF) += $(addsuffix .dtb, $(CONFIG_BUILTIN_DTB_NAME))
+
+# for CONFIG_OF_ALL_DTBS test
+dtb-	:= $(patsubst $(src)/%.dts,%.dtb, $(wildcard $(src)/*.dts))
diff --git a/arch/xtensa/boot/dts/csp.dts b/arch/xtensa/boot/dts/csp.dts
new file mode 100644
index 000000000..885495460
--- /dev/null
+++ b/arch/xtensa/boot/dts/csp.dts
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+
+/ {
+	compatible = "cdns,xtensa-xtfpga";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	interrupt-parent = <&pic>;
+
+	chosen {
+		bootargs = "earlycon=cdns,0xfd000000,115200 console=tty0 console=ttyPS0,115200 root=/dev/ram0 rw earlyprintk xilinx_uartps.rx_trigger_level=32 loglevel=8 nohz=off ignore_loglevel";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x40000000>;
+	};
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		cpu@0 {
+			compatible = "cdns,xtensa-cpu";
+			reg = <0>;
+		};
+	};
+
+	pic: pic {
+		compatible = "cdns,xtensa-pic";
+		#interrupt-cells = <2>;
+		interrupt-controller;
+	};
+
+	clocks {
+		osc: main-oscillator {
+			#clock-cells = <0>;
+			compatible = "fixed-clock";
+		};
+	};
+
+	soc {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "simple-bus";
+		ranges = <0x00000000 0xf0000000 0x10000000>;
+
+		uart0: serial@0d000000 {
+			compatible = "xlnx,xuartps", "cdns,uart-r1p8";
+			clocks = <&osc>, <&osc>;
+			clock-names = "uart_clk", "pclk";
+			reg = <0x0d000000 0x1000>;
+			interrupts = <0 1>;
+		};
+	};
+};
diff --git a/arch/xtensa/boot/dts/kc705.dts b/arch/xtensa/boot/dts/kc705.dts
new file mode 100644
index 000000000..6887ff090
--- /dev/null
+++ b/arch/xtensa/boot/dts/kc705.dts
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/include/ "xtfpga.dtsi"
+/include/ "xtfpga-flash-128m.dtsi"
+
+/ {
+	compatible = "cdns,xtensa-kc705";
+	chosen {
+		bootargs = "earlycon=uart8250,mmio32native,0xfd050020,115200n8 console=ttyS0,115200n8 ip=dhcp root=/dev/nfs rw debug memmap=0x38000000";
+	};
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x38000000>;
+	};
+
+	reserved-memory {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		/* global autoconfigured region for contiguous allocations */
+		linux,cma {
+			compatible = "shared-dma-pool";
+			reusable;
+			size = <0x04000000>;
+			alignment = <0x2000>;
+			alloc-ranges = <0x00000000 0x20000000>;
+			linux,cma-default;
+		};
+	};
+};
diff --git a/arch/xtensa/boot/dts/kc705_nommu.dts b/arch/xtensa/boot/dts/kc705_nommu.dts
new file mode 100644
index 000000000..d8e194a0f
--- /dev/null
+++ b/arch/xtensa/boot/dts/kc705_nommu.dts
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/include/ "xtfpga.dtsi"
+/include/ "xtfpga-flash-128m.dtsi"
+
+/ {
+	compatible = "cdns,xtensa-kc705";
+	chosen {
+		bootargs = "earlycon=uart8250,mmio32,0x9d050020,115200n8 console=ttyS0,115200n8 ip=dhcp root=/dev/nfs rw debug";
+	};
+	memory@0 {
+		device_type = "memory";
+		reg = <0x60000000 0x10000000>;
+	};
+	soc {
+		ranges = <0x00000000 0x90000000 0x10000000>;
+	};
+};
diff --git a/arch/xtensa/boot/dts/lx200mx.dts b/arch/xtensa/boot/dts/lx200mx.dts
new file mode 100644
index 000000000..974a8d904
--- /dev/null
+++ b/arch/xtensa/boot/dts/lx200mx.dts
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/include/ "xtfpga.dtsi"
+/include/ "xtfpga-flash-16m.dtsi"
+
+/ {
+	compatible = "cdns,xtensa-lx200";
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x06000000>;
+	};
+	pic: pic {
+		compatible = "cdns,xtensa-mx";
+		#interrupt-cells = <2>;
+		interrupt-controller;
+	};
+};
diff --git a/arch/xtensa/boot/dts/lx60.dts b/arch/xtensa/boot/dts/lx60.dts
new file mode 100644
index 000000000..7c203c1c7
--- /dev/null
+++ b/arch/xtensa/boot/dts/lx60.dts
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/include/ "xtfpga.dtsi"
+/include/ "xtfpga-flash-4m.dtsi"
+
+/ {
+	compatible = "cdns,xtensa-lx60";
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x04000000>;
+	};
+};
diff --git a/arch/xtensa/boot/dts/ml605.dts b/arch/xtensa/boot/dts/ml605.dts
new file mode 100644
index 000000000..08e5c8d47
--- /dev/null
+++ b/arch/xtensa/boot/dts/ml605.dts
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/include/ "xtfpga.dtsi"
+/include/ "xtfpga-flash-16m.dtsi"
+
+/ {
+	compatible = "cdns,xtensa-ml605";
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x08000000>;
+	};
+};
diff --git a/arch/xtensa/boot/dts/virt.dts b/arch/xtensa/boot/dts/virt.dts
new file mode 100644
index 000000000..611b98a02
--- /dev/null
+++ b/arch/xtensa/boot/dts/virt.dts
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+
+/ {
+	compatible = "cdns,xtensa-iss";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	interrupt-parent = <&pic>;
+
+	chosen {
+		bootargs = "console=ttyS0,115200n8 debug";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x80000000>;
+	};
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		cpu@0 {
+			compatible = "cdns,xtensa-cpu";
+			reg = <0>;
+			clocks = <&osc>;
+		};
+	};
+
+	clocks {
+		osc: osc {
+			#clock-cells = <0>;
+			compatible = "fixed-clock";
+			clock-frequency = <40000000>;
+		};
+	};
+
+	pic: pic {
+		compatible = "cdns,xtensa-pic";
+		/* one cell: internal irq number,
+		 * two cells: second cell == 0: internal irq number
+		 *            second cell == 1: external irq number
+		 */
+		#address-cells = <0>;
+		#interrupt-cells = <2>;
+		interrupt-controller;
+	};
+
+	pci {
+		compatible = "pci-host-ecam-generic";
+		device_type = "pci";
+		#address-cells = <3>;
+		#size-cells = <2>;
+		#interrupt-cells = <0x1>;
+
+		bus-range = <0x0 0x3e>;
+		reg = <0xf0100000 0x03f00000>;
+
+		     // BUS_ADDRESS(3)  CPU_PHYSICAL(1)  SIZE(2)
+		ranges = <0x01000000 0x0 0x00000000  0xf0000000  0x0 0x00010000>,
+			 <0x02000000 0x0 0xf4000000  0xf4000000  0x0 0x08000000>;
+
+		     // PCI_DEVICE(3)  INT#(1)  CONTROLLER(PHANDLE)  CONTROLLER_DATA(2)
+		interrupt-map = <
+			0x0000 0x0 0x0  0x1  &pic  0x0 0x1
+			0x0800 0x0 0x0  0x1  &pic  0x1 0x1
+			0x1000 0x0 0x0  0x1  &pic  0x2 0x1
+			0x1800 0x0 0x0  0x1  &pic  0x3 0x1
+			>;
+
+		interrupt-map-mask = <0x1800 0x0 0x0  0x7>;
+	};
+};
diff --git a/arch/xtensa/boot/dts/xtfpga-flash-128m.dtsi b/arch/xtensa/boot/dts/xtfpga-flash-128m.dtsi
new file mode 100644
index 000000000..c33932568
--- /dev/null
+++ b/arch/xtensa/boot/dts/xtfpga-flash-128m.dtsi
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/ {
+	soc {
+		flash: flash@00000000 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "cfi-flash";
+			reg = <0x00000000 0x08000000>;
+			bank-width = <2>;
+			device-width = <2>;
+			partition@0 {
+				label = "data";
+				reg = <0x00000000 0x06000000>;
+			};
+			partition@6000000 {
+				label = "boot loader area";
+				reg = <0x06000000 0x00800000>;
+			};
+			partition@6800000 {
+				label = "kernel image";
+				reg = <0x06800000 0x017e0000>;
+			};
+			partition@7fe0000 {
+				label = "boot environment";
+				reg = <0x07fe0000 0x00020000>;
+			};
+		};
+        };
+};
diff --git a/arch/xtensa/boot/dts/xtfpga-flash-16m.dtsi b/arch/xtensa/boot/dts/xtfpga-flash-16m.dtsi
new file mode 100644
index 000000000..7bde2ab2d
--- /dev/null
+++ b/arch/xtensa/boot/dts/xtfpga-flash-16m.dtsi
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/ {
+	soc {
+		flash: flash@08000000 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "cfi-flash";
+			reg = <0x08000000 0x01000000>;
+			bank-width = <2>;
+			device-width = <2>;
+			partition@0 {
+				label = "boot loader area";
+				reg = <0x00000000 0x00400000>;
+			};
+			partition@400000 {
+				label = "kernel image";
+				reg = <0x00400000 0x00600000>;
+			};
+			partition@a00000 {
+				label = "data";
+				reg = <0x00a00000 0x005e0000>;
+			};
+			partition@fe0000 {
+				label = "boot environment";
+				reg = <0x00fe0000 0x00020000>;
+			};
+		};
+	};
+};
diff --git a/arch/xtensa/boot/dts/xtfpga-flash-4m.dtsi b/arch/xtensa/boot/dts/xtfpga-flash-4m.dtsi
new file mode 100644
index 000000000..0655b8687
--- /dev/null
+++ b/arch/xtensa/boot/dts/xtfpga-flash-4m.dtsi
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/ {
+	soc {
+		flash: flash@08000000 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "cfi-flash";
+			reg = <0x08000000 0x00400000>;
+			bank-width = <2>;
+			device-width = <2>;
+			partition@0 {
+				label = "boot loader area";
+				reg = <0x00000000 0x003f0000>;
+			};
+			partition@3f0000 {
+				label = "boot environment";
+				reg = <0x003f0000 0x00010000>;
+			};
+		};
+	};
+};
diff --git a/arch/xtensa/boot/dts/xtfpga.dtsi b/arch/xtensa/boot/dts/xtfpga.dtsi
new file mode 100644
index 000000000..e46ae07ba
--- /dev/null
+++ b/arch/xtensa/boot/dts/xtfpga.dtsi
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0
+/ {
+	compatible = "cdns,xtensa-xtfpga";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	interrupt-parent = <&pic>;
+
+	chosen {
+		bootargs = "earlycon=uart8250,mmio32native,0xfd050020,115200n8 console=ttyS0,115200n8 ip=dhcp root=/dev/nfs rw debug";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x06000000>;
+	};
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		cpu@0 {
+			compatible = "cdns,xtensa-cpu";
+			reg = <0>;
+			clocks = <&osc>;
+		};
+	};
+
+	pic: pic {
+		compatible = "cdns,xtensa-pic";
+		/* one cell: internal irq number,
+		 * two cells: second cell == 0: internal irq number
+		 *            second cell == 1: external irq number
+		 */
+		#interrupt-cells = <2>;
+		interrupt-controller;
+	};
+
+	clocks {
+		clk54: clk54 {
+			#clock-cells = <0>;
+			compatible = "fixed-clock";
+			clock-frequency = <54000000>;
+		};
+	};
+
+	soc {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "simple-bus";
+		ranges = <0x00000000 0xf0000000 0x10000000>;
+
+		osc: main-oscillator {
+			#clock-cells = <0>;
+			compatible = "cdns,xtfpga-clock";
+			reg = <0x0d020004 0x4>;
+		};
+
+		serial0: serial@0d050020 {
+			device_type = "serial";
+			compatible = "ns16550a";
+			no-loopback-test;
+			reg = <0x0d050020 0x20>;
+			reg-shift = <2>;
+			reg-io-width = <4>;
+			native-endian;
+			interrupts = <0 1>; /* external irq 0 */
+			clocks = <&osc>;
+		};
+
+		enet0: ethoc@0d030000 {
+			compatible = "opencores,ethoc";
+			reg = <0x0d030000 0x4000 0x0d800000 0x4000>;
+			native-endian;
+			interrupts = <1 1>; /* external irq 1 */
+			local-mac-address = [00 50 c2 13 6f 00];
+			clocks = <&osc>;
+		};
+
+		i2s0: xtfpga-i2s@0d080000 {
+			#sound-dai-cells = <0>;
+			compatible = "cdns,xtfpga-i2s";
+			reg = <0x0d080000 0x40>;
+			interrupts = <2 1>; /* external irq 2 */
+			clocks = <&cdce706 4>;
+		};
+
+		i2c0: i2c-master@0d090000 {
+			compatible = "opencores,i2c-ocores";
+			#address-cells = <1>;
+			#size-cells = <0>;
+			reg = <0x0d090000 0x20>;
+			reg-shift = <2>;
+			reg-io-width = <4>;
+			native-endian;
+			interrupts = <4 1>;
+			clocks = <&osc>;
+
+			cdce706: clock-synth@69 {
+				compatible = "ti,cdce706";
+				#clock-cells = <1>;
+				reg = <0x69>;
+				clocks = <&clk54>;
+				clock-names = "clk_in0";
+			};
+		};
+
+		spi0: spi@0d0a0000 {
+			compatible = "cdns,xtfpga-spi";
+			#address-cells = <1>;
+			#size-cells = <0>;
+			reg = <0x0d0a0000 0xc>;
+
+			tlv320aic23: sound-codec@0 {
+				#sound-dai-cells = <0>;
+				compatible = "tlv320aic23";
+				reg = <0>;
+				spi-max-frequency = <12500000>;
+			};
+		};
+	};
+
+	sound {
+		compatible = "simple-audio-card";
+		simple-audio-card,format = "i2s";
+		simple-audio-card,mclk-fs = <256>;
+
+		simple-audio-card,cpu {
+			sound-dai = <&i2s0>;
+		};
+
+		simple-audio-card,codec {
+			sound-dai = <&tlv320aic23>;
+			simple-audio-card,bitclock-master = <0>;
+			simple-audio-card,frame-master = <0>;
+			clocks = <&cdce706 4>;
+		};
+	};
+};